16) ANNUAL REPORT 
special interest to note that some of these minerals are identical with 
those found in Portland cement. Five of these minerals have been found. 
The principal ones are: : | 
tst. A white crystalline mineral, high in lime, called alite, found in 
rapidly cooled basic hydraulic slags, and all Portland cements. 
2nd. A double refracting mineral showing distinct parallel stria- 
tions found in all slags and cements of inferior hydraulic value and show- 
ing a tendency to fall to a powder. ‘This is called felite. 
3rd. A glassy, usually dark-colored mass of good hydraulic value, 
in fact being equal to the alite in cementing quality. Of course, only the 
elass-like mass appearing in basic slags, and Portland cements, is meant 
here. The glassy constituent which predominates in acid slags has no hy- 
draulic properties. Cuenched basic slags show this glassy component in 
predominating quantity. 
Zulkowski assumed that the hydraulic mineral varieties of basic 
slags are preserved only by rapid cooling, while on slow cooling they 
break down to simpler non-hydraulic compounds. This agrees 
very well with practical results, inasmuch as we know that frequently 
Portland cement mixtures produce excellent cements when burnt rapidly, 
but “dust” or form a slightly hydraulic powder when burnt slowly. 
This cement producing constituent, whether found in slags or Port- 
land cements, Zulkowski called “hydrolite,’ which as we now know 
consists essentially of alite or cement glass, or both. 
By treatment with dilute acid Zulkowski endeavored to separate the 
constituents of the slowly and rapidly cooled slags which, of course, is a 
crude and unsatisfactory procedure, and his earlier results based on this 
work deserve little attention. But he brought out the very interesting fact 
that quenched basic slag, though possessing cement qualities, brings out 
its inherent maximum hydraulic value only when mixed with a small per- 
centage of slaked lime. Zulkowski now looked into this question by 
treating granulated slag not only with lime, but also with strontium, 
barium, and alkalies. All of these showed the same behavior, and caused 
the slag to become a good cement. It was also found that the compound 
thus added did not combine chemically with the slag itself. Thus, for 
instance, the alkalies could be washed out from the hardened cement 
after they had caused the slag to harden. Water alone evidently is the 
reacting substance in uniting with the hydrolite to form a hydrous sili- 
cate. Caustic lime simply accelerates and assists this absorption. Very 
basic slags do not need an addition of lime. Having arrived at this con- 
clusion, Zulkowski at once was able to trace the analogy between slag and 
Portland cement by saying that the latter consists of the same hydrolite 
as the slag cement plus free lime. Portland cement, therefore, like very 
basic slag, does not need an addition of lime. 
On experimenting with the slag, which alone hardens slowly in water, 
it was found by means of the microscope that it consisted of small glitter- 
